Endotracheal intubation is a common medical procedure. Endotracheal tubes are used in many situations. They are used as conduits for airway life support where patients have stopped breathing on their own (e.g., because of cardiac arrest, respiratory distress/arrest, seizures, and the like). They are also used in both human and animal surgery to provide passageways for anesthetic gases into lungs.
Endotracheal tubes are typically made of soft biomaterials. The most common biomaterial is polyvinyl chloride with a plasticizer added, but other synthetic materials are either currently used or are being developed. The endotracheal tube made of this soft material is difficult to manipulate and insert into the trachea (windpipe). A malleable stylette is often placed into a central lumen of an endotracheal tube to provide more rigidity to the tube and allow the caregiver to have better control during the tube's insertion. In practice, the added stiffness allows the caregiver to easily guide the distal end of the endotracheal tube between vocal cords and into a patient's trachea. Typically, such stylettes are malleable rods made of plastic or a plastic-coated soft metal. Normally, the stylette is inserted the length of the endotracheal tube's central lumen to a point just before the endotracheal tube ends. After the endotracheal tube is inserted into the trachea, the stylette is immediately removed.
Typically, the oral insertion of an endotracheal tube occurs while the patient lies on the back and the neck is slightly extended with the nose in a sniffing position. A caregiver, using his left hand to hold a laryngoscope, inserts the laryngoscope into the right corner of the mouth and advances its tip to the depth of the esophagus (swallowing tube into the stomach). The caregiver uses the laryngoscope to displace the tongue to the left side of the mouth, out of the way and providing a line-of-sight into the deepest portion of the patient's throat. This line-of-sight extends into the patient's esophagus, which is a large, wide, funnel-shaped structure. The laryngoscope is withdrawn from the esophagus until the patient's epiglottis and vocal cords (which define an entrance into the patient's trachea) come into view. The epiglottis and the vocal cords lie in front of and above the esophagus. The caregiver then inserts the distal end of the endotracheal tube through the vocal cord opening and into the trachea. After the endotracheal tube is properly positioned in the patient's trachea, the tube is secured to the patient's lip (e.g., with tape or a device).
The caregiver cannot see the distal end of an endotracheal tube after it has been inserted through the vocal cords. Consequently, it is difficult to determine the ultimate depth of insertion. Thus, the caregiver uses a reference mark on the tube that can be seen inside the mouth and that indicates the proper depth of insertion. Also, during prolonged periods of intubation that provide assisted breathing, it is difficult to tell if the endotracheal tube has moved from its initial, secured position. Inserting an endotracheal tube too far into the patient can be hazardous. For example, if an endotracheal tube extends beyond the carina (i.e., the point at which the trachea branches into the right and left lung) and into the patient's right mainstem bronchus, the bronchial intubation can result in injury.
Right mainstem bronchial intubation (RMSBI) can cause the complications listed below or even death of the patient. This is especially true with respect to small patients such as neonates. RMSBI is a potential cause of morbidity during neonatal assisted ventilation (breathing). RMSBI can cause overdistention of the right middle and/or lower lobes of the lung and underventilation and/or atelectasis of the remaining lung (cited in Kuhns L. R. and Poznanski A. Endotracheal position in the infant. J Pediatr 1971;78:991-6; Kattwinkel J. Textbook of Neonatal Resuscitation. 4th ed., Elk Grove Village: American Academy of Pediatrics and American Heart Association; 2000, p. 5-27). If inflation of a pulmonary lobe is excessive, lobar emphysema, pulmonary interstitial emphysema, pneumothorax, and/or pneumomediastinum may occur (cited in Thibeault D. W., Lachman R. S., and Kwong M. S. Pulmonary interstitial emphysema, pneumomediastinum, and pneumothorax in the newborn infant. Am J Dis Child 1973;126:611-4).
The risk of RMSBI in neonates is high relative compared to larger patients because the distance from the larynx (vocal cords) to the carina is relatively reduced in newborn infants. The endotracheal tubes that are used for intubation of newborn infants are also smaller than those used with larger patients. FIG. 1, for example, shows the tubular portion of an endotracheal tube. The tubular portion shown in FIG. 1 has a length on the order of an adult finger. If the patient has a weight of, for example, 1 to 2 pounds, the acceptable positioning of the distal end of the endotracheal tube within the trachea may only be an up and down distance of about 0.25 to 0.5 inches. Thus, the margin for error when inserting and maintaining an endotracheal tube in neonates is especially small.
Today, more extremely low birth weight infants (<1000 g) are treated with assisted ventilation. As medical technology continues to improve the survival rate of preterm neonates, there is a need to reduce the problems associated with endotracheal intubation in preterm and term newborn infants. There is also a need to reduce the problems associated with intubation of other patients such as toddlers and adults.
Accordingly, improved endotracheal tubes and methods for using the same would be desirable. Embodiments of the invention address the above noted problems and other problems, individually and collectively.